You mean miner fees? How's that a 100% margin after hardware and electricity? Sure if the network transfers to a PoS/ETH2 model those operating costs go down, but so will transaction fees, hence revenue, with the planned sharding, transaction wrapping/bundling (I'm forgetting the terminology here) and burning, no? It also seems necessary to gut those transaction costs if ETH wants to be useful. Even then, that staking model isn't exactly costless either for nodes, they do have to freeze assets therefore giving it opportunity cost and making their goods highly illiquid.

I'd add, if your revenue figure is right, 12B profit (let's be generous) isn't exactly something to drool about on a 250B base. A 5% yield is of course fine if sustainable, arguably high end (in line with sectors like oil, but below sin sectors and specific stocks), but I'd bet 5% is not the sort of returns the crypto crowd is aiming for, not even close. There are safer ways to earn 5%.